The Prognostic Role of Mitotic Index in Hepatocellular Carcinoma Patients after Curative Hepatectomy

PURPOSE: High proliferation rate is a hallmark of cancer. The mitotic index is a useful and simple method for analysis of cell proliferation. However, the practical utility of mitotic index as a predictor of prognosis in patients with hepatocellular carcinoma (HCC) has not been determined. Therefore, we examined mitotic index as a prognostic marker in HCC patients. MATERIALS AND METHODS: We counted the number of mitotic cells in 10 high-power fields of the tumor area on hematoxylin and eosin–stained slides representing 282 surgically resected HCCs. The highest number of mitotic cells was defined as the mitotic index. RESULTS: High mitotic index was observed in 127 of 282 HCCs. High mitotic index showed significant association with younger age, larger tumor size, higher Edmondson grade, microvascular invasion, major portal vein invasion, intrahepatic metastasis, higher American Joint Committee on Cancer (AJCC) T-stage, higher Barcelona Clinic Liver Cancer (BCLC) stage, higher alpha-fetoprotein level, hepatitis B virus etiology, and liver cirrhosis. Patients with high mitotic index had shorter disease-specific survival (DSS) (p < 0.001) and tended to have shorter recurrence-free survival (p=0.112). In subgroup analysis among patients with a larger tumor size, microvascular invasion, intrahepatic metastasis, higher AJCC T-stage, and higher BLCL stage, high mitotic index showed unfavorable influences on DSS (p=0.001, p=0.008, p=0.003, p=0.012, and p < 0.001, respectively). In addition, high mitotic index was an independent predictor of shorter DSS (p=0.004). CONCLUSION: High mitotic index may be a novel predictor of DSS in patients with HCC and may have utility as an auxiliary prognostic factor in HCC.